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Old 23-03-2013, 06:55   #1
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Battery charging question

I have 8 Trojan T105s wired series/parallel to produce a 900ah 12v house bank. I am charging with a pair of Xantrex 1260s combined by the Remote Panel to give me 120 amps total charge current.
Trojan T105 specs the daily charge (absorption) volts at 14.8v. The Xantrex spec shows an absorption of 14.4v. Am I correct in assuming that I am never getting a full charge to my house bank?
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Old 23-03-2013, 07:23   #2
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Re: Battery charging question

I wouldn't assume anything. I would verify it by checking the specific gravity!

But you charging at a lower voltage and my experience last year was that it does not result in the batteries charging fully, regardless of what the voltage says afterwards.

I would check that you have flood wet cell batteries selected as type if your charger has different settings. You should also check this for your alternator regulator.

if you can not increase the voltage you may just need to do more frequent equalizing charges.

Trojan Battery Company
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Old 23-03-2013, 09:36   #3
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Re: Battery charging question

http://www.trojanbattery.com/pdf/TRJ...UsersGuide.pdf

Page 13. Absorption 14.1-14.7 volts. You're good to go.
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Old 23-03-2013, 10:16   #4
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Re: Battery charging question

Higher voltage means more current so you get the amp-hours into the battery with fewer hours.
Lower voltage means less current so it will take more hours to get the amp-hours into the battery.
So long as current is flowing in you are storing (most of) it so it is charging and will eventually get a full charge.
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Old 23-03-2013, 12:14   #5
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Re: Battery charging question

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Originally Posted by Andina Marie View Post
Higher voltage means more current so you get the amp-hours into the battery with fewer hours.
Lower voltage means less current so it will take more hours to get the amp-hours into the battery.
So long as current is flowing in you are storing (most of) it so it is charging and will eventually get a full charge.

I spoke with a Trojan tech who said basically the same thing. He said I needed to get the absorption voltage up to at lease 14.7v to shorten the charge time. Right now if I am approximately 200 ah down on the battery monitor, I have to run the generator for about 8 to 9 hours to get the monitor to show full.
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Old 23-03-2013, 13:24   #6
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Re: Battery charging question

you should maybe look into your charger settings to see if you can increase the time of the bulk charge phase
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Old 23-03-2013, 14:29   #7
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Re: Battery charging question

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you should maybe look into your charger settings to see if you can increase the time of the bulk charge phase
Xantrex says no. So I guess I'm going to have to look at a better charger. Anybody got recommendations on a good charger of about 120 amps that the charge parameters are user-adjustable? Hopefully I will soon have two nearly new Xantrex 1260s and a remote panel for sale.
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Old 23-03-2013, 14:34   #8
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Re: Battery charging question

Victron chargers/inverters are excellent quality and let you adjust the various voltages and amps for bulk, absorption and float. My current one will charge at 120Amps @ 24V and the inverter provides power for a bevy of blondes to all use hair-driers aboard Seriously, Victron products are high-quality and there are various charger and charger/inverter models to choose from.
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Old 23-03-2013, 14:41   #9
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Re: Battery charging question

Charging your batteries up to 100% charge with a generator is really tough. That is why people use solar. Charge the batteries in the morning with the gen. while preparing coffee/breakfast and then let the solar cells bring them further up during the day, hopefully to a full charge. Once a month, at least, make sure you get them fully charged. That last 15% is what is taking you the most time.
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Old 23-03-2013, 15:03   #10
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Re: Battery charging question

Do your chargers have a separate voltage sensing wire connected to the batteries? How much are you willing to play around with electronics?

A Schottky diode placed in the voltage sensing line will drop the voltage sensed by the charger by about 0.4 to 0.5V. That would make the charger think 14.8 was 14.3 to 14.4 (depending on the diode selected). Lots easier than changing everything out, I would feel comfortable with it but would also monitor carefully for the first little while.

[EDIT]

Links to diodes with 0.35-0.45V forward voltage:

Search results for "" - Allied Electronics

A possible selection (0.385V, can handle 0.5A, cost is 11 cents):

ON Semiconductor - MBR0520LT1G - Semiconductors - Diodes - Allied Electronics

[/EDIT]
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Old 23-03-2013, 15:20   #11
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Re: Battery charging question

With 2 x 2 x T105s I put my solar controller on 14.8V and left Boracay for 4 months. When I came back the water level in the batteries was pretty well down to the minimum but (from memory) the batteries were well charged.

Last time I left I put the controller on 13.2V and three months later water levels are unchanged but the batteries were not fully charged.

So I'm thinking that 14.8V would be fine as long as there is some sort of appropriate load and water levels were checked regularly, but that with no load I',m better off at something like 14.0V.

At the moment my high voltage cut off is set at 14.4V.
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Old 23-03-2013, 15:54   #12
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Re: Battery charging question

Quote:
Originally Posted by Dsanduril View Post
Do your chargers have a separate voltage sensing wire connected to the batteries? How much are you willing to play around with electronics?

A Schottky diode placed in the voltage sensing line will drop the voltage sensed by the charger by about 0.4 to 0.5V. That would make the charger think 14.8 was 14.3 to 14.4 (depending on the diode selected). Lots easier than changing everything out, I would feel comfortable with it but would also monitor carefully for the first little while.

[EDIT]

Links to diodes with 0.35-0.45V forward voltage:

Search results for "" - Allied Electronics

A possible selection (0.385V, can handle 0.5A, cost is 11 cents):

ON Semiconductor - MBR0520LT1G - Semiconductors - Diodes - Allied Electronics

[/EDIT]
That's a great idea but unfortunately the Xantrex 1260 does not use a voltage sensing input. The Link Lite battery monitor does, but not the chargers. It was cool seeing the Allied logo in the link you posted. I haven't ordered anything from them since I was a kid messing around with tube-type gear.
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Old 23-03-2013, 16:21   #13
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Re: Battery charging question

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Originally Posted by F51 View Post
Xantrex says no. So I guess I'm going to have to look at a better charger. Anybody got recommendations on a good charger of about 120 amps that the charge parameters are user-adjustable? Hopefully I will soon have two nearly new Xantrex 1260s and a remote panel for sale.
Sterling power make a truly excellent charger. It has both a good wet cell stock program, but is also as adjustable if you want.

One thing I like is that it has an easy to use and adjustable equalization cycle. It's also very efficient . . . I can run much more 12vt amps without stalling the Honda gen.

I use one with a bank very similar to yours - 8 x T105s house + 2 x t 105s start. The batteries are much happier than with the two prior chargers.
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Old 23-03-2013, 17:03   #14
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Re: Battery charging question

Quote:
Originally Posted by F51 View Post
I have 8 Trojan T105s wired series/parallel to produce a 900ah 12v house bank. I am charging with a pair of Xantrex 1260s combined by the Remote Panel to give me 120 amps total charge current.
Trojan T105 specs the daily charge (absorption) volts at 14.8v. The Xantrex spec shows an absorption of 14.4v. Am I correct in assuming that I am never getting a full charge to my house bank?
Absolutely correct. Read Handy Bob Solar web site. Bob has experimented with this, he is an electrical engineer. He has seriously strong opinions about the poor relation between the people who set up chargers and the battery makers. Nearly all chargers according to Bob are under the necessary voltage and prematurely cratering the batteries.

HandyBob's Blog Making off grid RV electrical systems work its a long read but worth it. I re-read it every time I start a new project. Lots of fundamentals to DC battery systems & not all solar related.
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Old 24-03-2013, 07:29   #15
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Re: Battery charging question

Quote:
Originally Posted by Nicholson58 View Post
Absolutely correct. Read Handy Bob Solar web site. Bob has experimented with this, he is an electrical engineer. He has seriously strong opinions about the poor relation between the people who set up chargers and the battery makers. Nearly all chargers according to Bob are under the necessary voltage and prematurely cratering the batteries.

HandyBob's Blog Making off grid RV electrical systems work its a long read but worth it. I re-read it every time I start a new project. Lots of fundamentals to DC battery systems & not all solar related.
Was a good read with good stuff in it, but it was loooooooooong!
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