Charging multiple glider batteries

[Don[_4_]]

Our club (US) keeps 8 batteries charged in two banks of 4 batteries. We
use two Battery Tender Junior chargers, one for each bank. The charging
rate is not very fast, but they have at least 20 hours between use and
often a week. Mostly this has worked pretty well, but we are more often
finding batteries that are not fully charged, even though the battery
tender is green indicating full charge. Once fully charged, the charger
just floats them. The batteries are the popular glider batteries, 12
volt 7 amp hour sealed lead acid.

How do other clubs, commercial ops keep multiple batteries charged up?

I realize charging problems can occur when one battery is damaged, won't
take a full charge or is simply dead. Or if the charging rate varies
markedly from batt to batt. It may be possible to overcharge the other
ones. Ideally each battery would be charged individually, but that is
expensive and takes more space. What solutions are out there?

[Martin Gregorie[_5_]]

On Mon, 06 Jan 2014 14:53:37 -0500, Don wrote:

> Our club (US) keeps 8 batteries charged in two banks of 4 batteries. We
> use two Battery Tender Junior chargers, one for each bank. The charging
> rate is not very fast, but they have at least 20 hours between use and
> often a week. Mostly this has worked pretty well, but we are more often
> finding batteries that are not fully charged, even though the battery
> tender is green indicating full charge.
>
Are you sure that charging a number of batteries in parallel isn't
confusing the charger and causing it to switch to the next phase earlier
than it should?

> How do other clubs, commercial ops keep multiple batteries charged up?
>
I carry two batteries, one running T&B and radio, the other driving both
varios and a satnav running LK8000 and I use a pair of mains powered
Sunpower UK two-phase SLA chargers to charge them. Unsurprisingly, they
have differing charge states after flying and, as a result, there is
usually a large time difference between the two chargers signalling that
they are in float mode.

My club has, I think, nine batteries for the club fleet, which are
charged by a set of mains powered two-phase SLA chargers, one per
battery. When they are not in gliders, the batteries are permanently
connected to their individual chargers, which look to be in the same
performance and price range as the ones your club uses.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Vaughn]

On 1/6/2014 2:53 PM, Don wrote:
> Ideally each battery would be charged individually, but that is
> expensive and takes more space.
The excellent Battery Tender Jr. is available for around $23.00. You
can put four of them on a cheap power strip to charge a bank of
batteries and you will have spent less than $100.00 to properly charge
each bank of your batteries. That's too bulky and expensive? Really?

Also, SLA batteries don't improve with age. If ever left discharged,
they go bad very quickly. A bad battery looks exactly the same as a
good one. Some of yours may need replacing.

Hint: Because the capacity of a battery decreases over time, one symptom
of a bad battery you might notice is that it takes a charge much quicker
than a good one.

Vaughn

[Eric Greenwell[_4_]]

Vaughn wrote, On 1/7/2014 6:11 AM:
>
> Hint: Because the capacity of a battery decreases over time, one symptom
> of a bad battery you might notice is that it takes a charge much quicker
> than a good one.

A weak battery, unless it was run completely flat, will take just as
long to charge as good battery that was discharged the same amount. You
have to replace the amp hours you took out, regardless of the capacity
of the battery.

What tells you your battery has lost capacity is it won't power your
instruments as long as it used to, or the voltage is significantly lower
after a flight than when it was new. You can also do a discharge test to
determine the capacity, using a resistance and a voltmeter (cheap), or a
device designed to do it automatically ($50-$150 range for that).

Regardless, considering the low cost of a decent 800 ma charger, I'd go
the "one charger per battery" route.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

[Vaughn]

On 1/7/2014 10:04 AM, Eric Greenwell wrote:
> A weak battery, unless it was run completely flat, will take just as
> long to charge as good battery that was discharged the same amount. You
> have to replace the amp hours you took out, regardless of the capacity
> of the battery.

OK, I should have said "A flat bad battery will charge quicker than a
flat good battery" precisely because you need to put fewer amp hours
into the bad battery before it is fully charged.

What fills quicker from the same tap, a large cup or a shot glass?

I have heard many folks say something like "that battery must be good
because it takes a good charge in no time at all."

Vaughn

[Soartech]

>
> The excellent Battery Tender Jr. is available for around $23.00. You
>
> can put four of them on a cheap power strip to charge a bank of
>
> batteries and you will have spent less than $100.00 to properly charge
>
> each bank of your batteries.

For even less you can get a similar small battery charger at Harbor Freight.
They are $10 but are often on sale with a coupon for less.

http://www.harborfreight.com/automatic-battery-float-charger-42292.html

[[email protected]]

On Tuesday, January 7, 2014 9:38:19 AM UTC-8, Soartech wrote:

> > The excellent Battery Tender Jr. is available for around $23.00. You
> > can put four of them on a cheap power strip to charge a bank of
> > batteries and you will have spent less than $100.00 to properly charge
> > each bank of your batteries.
> For even less you can get a similar small battery charger at Harbor Freight.
>
> They are $10 but are often on sale with a coupon for less.
> http://www.harborfreight.com/automatic-battery-float-charger-42292.html

A good battery tester helps. I recently got one and discovered that the charger I bought when I got my glider 10 years ago only puts 6 Ah into my 10.5 Ah SLA batteries. A different charger gets them up to about 7-8 Ah for my load profile. I've been running tests on some 9 Ah LiFePo4 batteries as well - pretty impressive performance so far - better than the 10.5 Ah SLA. I'll share results after I've had a chance to test them in my fridge.

9B

[Brian[_1_]]

1st question is how old are the batteries? Under ideal conditions they are probably going to lose about 10% of their capacity within 3 years and 20% by 4 years. (Powersonic DataSheet) I typically replace my batteries every two years but have gone 3 to 4 years depending on how they are performing. Glider usage, could hardly be consider ideal usage for them so less life expectancy isn't uncommon.

Contrary to what seems to be popular opinion, I really don't see a problem with the parallel charging (especially with a low current charger) as long as your trickle charging is holding or bringing the voltage to between 13.5 and 13.8 volts. Use a meter and test this.

I will agree that a bad or weak battery may prevent the other batteries from charging properly, but then again this is really a battery problem not a charger problem.


Brian

[bumper[_4_]]

On Tuesday, January 7, 2014 9:38:19 AM UTC-8, Soartech wrote:

>
> For even less you can get a similar small battery charger at Harbor Freight.
>
> They are $10 but are often on sale with a coupon for less.
>
>
>
> http://www.harborfreight.com/automatic-battery-float-charger-42292.html

I'm almost always in favor of "for even less!". But in this case I gotta give HF's offering a double thumbs down - I threw them in the trash. Of the two examples I purchased, both appear ed to be non-temperature compensated constant voltage chargers that would not fully charge a 7 AH battery in good condition. Max float charge voltage was under 13 volts IIRC. Spend the extra and get chargers at least as good or better than "Battery Tenders".

http://batterytender.com/resources/float-charging.htm/

bumper

[[email protected]]

> How do other clubs, commercial ops keep multiple batteries charged up?
>

I made this circuit some 15 years ago:
http://www.johny.dk/Soaring/Akku%20Lader.html
and put 8 of these into a 19 inch cabinet, one circuit per battery. It gives good feedback as to the state of the batteries: Too fast blinking frequency->its time to contact your battery dealer.

Johny

[Don[_4_]]

Lots of good input from you all. We will definitely make some changes
now. Will check the condition of each battery under load, cull out the
worst and then probably use a separate charger for each battery. Thanks
to all, but we will be watching to see if any other comments come in
before getting started. Don.

[Vaughn]

On 1/7/2014 12:38 PM, Soartech wrote:
> For even less you can get a similar small battery charger at Harbor Freight.
> They are $10 but are often on sale with a coupon for less.
>
> http://www.harborfreight.com/automatic-battery-float-charger-42292.html

Because of HF's lack of quality control, I would hesitate to recommend
these. That said, I have used two of them with good results. One of
them I used for several years!

Vaughn

[Brian[_1_]]

From the Battery Tender Web Site.... Short version, yes it is OK to charge the same voltage batteries in Parallel....

Can the Battery Tender® Plus battery charger be used to charge more than 1 battery simultaneously if the batteries are connected in parallel?

Yes, but with restrictions. A parallel connection means that positive posts of each battery are electrically connected together and the negative posts of each battery are electrically connected together. The voltage of a parallel connected battery pack is exactly the same as the voltage of each battery in that pack.

If the nominal battery voltages (i.e. 12V, 8V, 6V) are the same on each battery, and if the batteries are the same lead acid type (flooded, AGM, or Gel Cell), then yes, the Battery Tender® Plus battery charger can be used to charge more than 1 battery simultaneously when those batteries are connected in parallel. Just remember that 2 batteries in parallel behave like one large battery. The charge storage capacity of each battery simply adds together. Two 12 volt batteries, each with 25 amp hour capacities, will look like one 12 volt battery with a 50 amp hour capacity. You may be able to charge more than 1 battery simultaneously, but it will take longer to do it.

[Mike J.]

On Monday, January 6, 2014 1:53:37 PM UTC-6, Don wrote:
> Our club (US) keeps 8 batteries charged in two banks of 4 batteries. We use two Battery Tender Junior chargers, one for each bank. The charging rate is not very fast, but they have at least 20 hours between use and often a week. Mostly this has worked pretty well, but we are more often finding batteries that are not fully charged, even though the battery tender is green indicating full charge. Once fully charged, the charger just floats them. The batteries are the popular glider batteries, 12 volt 7 amp hour sealed lead acid. How do other clubs, commercial ops keep multiple batteries charged up? I realize charging problems can occur when one battery is damaged, won't take a full charge or is simply dead. Or if the charging rate varies markedly from batt to batt. It may be possible to overcharge the other ones. Ideally each battery would be charged individually, but that is expensive and takes more space. What solutions are out there?

[Neil Allison]

Hi Don,

> How do other clubs, commercial ops keep multiple batteries charged up?

I built a 1Ux19" rack mount, 12-way charger for the Canterbury Gliding Club. Batteries remain connected to the charger whenever they are not in a glider. The charger uses Silvertel Ag102 multi-stage battery charger modules, one per battery.

Each channel has a green LED that is illuminated when the battery has returned to float charging. The idea is to help club members identify which batteries have just been connected and which have been recharged.

These photos are from my workshop during testing:
http://www.avon-tech-solutions.co.nz/images/12WCharger_Rack.JPG
http://www.avon-tech-solutions.co.nz/images/12WCharger.JPG

On our flying camps at Omarama, we take a couple of 4-outlet versions that are powered by a laptop AC adapter:
http://www.avon-tech-solutions.co.nz/gliding.html

When I test batteries I do a semi-automatic, timed discharge to 10.5V using a 50W 12V halogen light bulb. If this duration is less than about 75% of the nominal Ah value I suggest the battery is replaced.

--
Neil Allison
Christchurch, NZ

[Martin Gregorie[_5_]]

On Mon, 06 Jan 2014 23:05:00 +0000, Tim Newport-Peace wrote:

> There are meters which will measure battery capacity, but cost more than
> 6 batteries, so probably not an option. I have used one for many years,
> but I bought it as a work tool where it pays for itself.
>
Tim,

Battery checkers are cheaper that you may think if you look in the right
places. I think that means model shops.

I have a Pro-Peak Prodigy II that charges and cycles NiCd, NiMH, Li-poly/
ion and SLA batteries. It runs off 12v and but can charge and cycle cell
stacks of up to 18v. You get to set the chemistry, charge and discharge
rates and, after the cycle is complete, it gives a read-out of both
charge and discharge capacity. The current Pro-Peak model has similar
capabilities and sells for just under £55.

Pure capacity checkers run £15-£20 though you'd have to hunt round
because most only deal with Li-poly/ion or LiFe batteries. However,
you'd want one that can deal with NiCd, NiMH or SLA because the per-cell
cut-off point for Li-poly/ion is normally 3.1v/cell.

I prefer to use Yuasa NP7-12L SLA batteries. The current cost is £16.80
including VAT and shipping, so the price of model flying cyclers and
testers doesn't look all that far out of line with the price of these
batteries.



--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Martin Gregorie[_5_]]

On Tue, 07 Jan 2014 23:10:31 +0000, Tim Newport-Peace wrote:

>>Battery checkers are cheaper that you may think if you look in the right
>>places. I think that means model shops.
>>
>>I have a Pro-Peak Prodigy II that charges and cycles NiCd, NiMH,
>>Li-poly/
>>ion and SLA batteries. It runs off 12v and but can charge and cycle cell
>>stacks of up to 18v. You get to set the chemistry, charge and discharge
>>rates and, after the cycle is complete, it gives a read-out of both
>>charge and discharge capacity. The current Pro-Peak model has similar
>>capabilities and sells for just under £55.
>>
>>Pure capacity checkers run £15-£20 though you'd have to hunt round
>>because most only deal with Li-poly/ion or LiFe batteries. However,
>>you'd want one that can deal with NiCd, NiMH or SLA because the per-cell
>>cut-off point for Li-poly/ion is normally 3.1v/cell.
>>
>>I prefer to use Yuasa NP7-12L SLA batteries. The current cost is £16.80
>>including VAT and shipping, so the price of model flying cyclers and
>>testers doesn't look all that far out of line with the price of these
>>batteries.
>>
>>
>>
> The one I use is Actmeter IBT tester.
> http://www.actmeters.com/battery-testing/gold-plus-6v-12v-battery-tester
>
> Testers that need to do full charge/discharge cycles are no use to me
> when I have a customer with about 200 NP7-12 batteries installed.
>
Fair comment, but I was looking at something that an individual or club
might use to check a few batteries once a year. Any of the Pro-peak
chargers or their equivalents are perfectly adequate for that duty cycle.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[GC[_2_]]

Very neatly executed!

I assume the vertical boards are the Ag102 and the horizontal ones are
your I/O circuits. Is that right? What did you need to add?

The Shortform doc says the charger IS temperature-compensated but also
says that "With the addition of a low-cost thermistor, charge voltages
CAN be temperature compensated". Which is right? Did you have to add a
thermistor yourself?

Is there an NZ/Oz distributor for Silvertel?

GC


On 8/01/2014 09:01, Neil Allison wrote:
> Hi Don,
>
>> How do other clubs, commercial ops keep multiple batteries charged up?
>
> I built a 1Ux19" rack mount, 12-way charger for the Canterbury Gliding Club. Batteries remain connected to the charger whenever they are not in a glider. The charger uses Silvertel Ag102 multi-stage battery charger modules, one per battery.
>
> Each channel has a green LED that is illuminated when the battery has returned to float charging. The idea is to help club members identify which batteries have just been connected and which have been recharged.
>
> These photos are from my workshop during testing:
> http://www.avon-tech-solutions.co.nz/images/12WCharger_Rack.JPG
> http://www.avon-tech-solutions.co.nz/images/12WCharger.JPG
>
> On our flying camps at Omarama, we take a couple of 4-outlet versions that are powered by a laptop AC adapter:
> http://www.avon-tech-solutions.co.nz/gliding.html
>
> When I test batteries I do a semi-automatic, timed discharge to 10.5V using a 50W 12V halogen light bulb. If this duration is less than about 75% of the nominal Ah value I suggest the battery is replaced.
>

[Neil Allison]

> Very neatly executed!

Thank you.

> I assume the vertical boards are the Ag102 and the horizontal ones are
> your I/O circuits. Is that right? What did you need to add?

Correct. XLR rack mount panel is from Jaycar. I chose to use a microcontroller to detect and signal float conditions: one 8pin ATiny13 and its associated 5V supply and voltage sensing parts does a pair of charger channels. I resisted the temptation to indicate bulk and absorption charging state by flashing the LED at different rates (except as an experiment during development).

> The Shortform doc says the charger IS temperature-compensated but also
> says that "With the addition of a low-cost thermistor, charge voltages
> CAN be temperature compensated". Which is right? Did you have to add a
> thermistor yourself?

Yes, you do need to add the NTC: one per channel. I chose not to temp comp because of the perceived challenge of measuring the (correct) battery temperature in a club situation. But I left provision on my pcb to provide temp comp.

> Is there an NZ/Oz distributor for Silvertel?

Fairmont Marketing. www.semiconductorstore.com also ship down here.

Cheers
Neil