Charging multiple glider batteries

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

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)

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

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/automat...ger-42292.html

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/automat...ger-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

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/automat...ger-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

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/automat...ger-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