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Author Topic: where to buy deep cycle batteries?  (Read 2745 times)
guydewdney
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« on: August 25, 2015, 07:22:14 PM »

The batteries in my monster motorhome (33 foot long ten tons) requires 24v, as many Ah as i can fit in the space, and needs to supply two major components, a marine fridge (approx 20ah per day) and a disabled lift (ten seconds at 40 amps each time).

An online store is listing 4 x t105 trojan batteries making 225ah for 400 smackers. Or £1.77 per ah rating.

Is this good?

The space is 550w x 500d x 400h

Suggestions please.

Guy
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ceisra
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« Reply #1 on: August 25, 2015, 07:33:48 PM »

I use this outfit http://www.batterymegastore.co.uk/
They have always been cheaper than any one else.   
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Scruff
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« Reply #2 on: August 25, 2015, 08:12:38 PM »

Trojans are pretty good. Everytime I go oogling a scissorlift gubbins I find a set. It's hard to beat the price of the T-105s
I think Crown are better but I have no evidence to support it except they weigh more.
They meet their ratings which is good by standards.

It's a good price.
I'd go one or thuther if I couldn't fit forklifts.


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guydewdney
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« Reply #3 on: August 25, 2015, 08:21:38 PM »

There's little in the price, but would 4 x12v be better than 4 x 6v? I have 12v and 24v chargers. Example i can fit 4 x 27tmx batteries, wired series parallel, but if a cell went south, then at least i have 105ah @24v left if i disconnected one half. If a cell went down on the 4 bank of 6, im stuffed. The lift is almost safety critical (there is a slow hand pump) but would work i suspect at 18v

Answer to my own question
http://forum.solar-electric.com/forum/solar-electric-power-wind-power-balance-of-system/general-solar-power-topics/13179-series-rule-of-thumb?14674-Series-rule-of-thumb=

« Last Edit: August 25, 2015, 10:01:24 PM by guydewdney » Logged

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Scruff
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« Reply #4 on: August 25, 2015, 10:05:14 PM »

I was thinking along the same lines myself last time I had a battery refit. I went from 2 x 12v to 2 x 6v. Because my 12vs died a death after a life of hardships and were retired at about 50% capacity.
From the research I did the TMX can hold their own too. Problem with other 12v leisure batteries is they're most often just relabelled starter batteries whereas 6 volt are reliably deep cycle batteries as they have no application to be otherwise. Anything with a comparably high CCA or MCA to the Ah rating is usually a mislabelled starter battery. As I recall the TMX are more costly per watt than the T-105.

The benefit of the 6v is that it's much easier swap the weak cells to the centre of the bank. As far as I've seen it's always the outer cells that get worked the hardest ie. the one tied to the -ive post and the one tied to the +ive post whereas the ones in the middle have a much easier life.

You can get more watts in the same package with a T-125 or T-145 but the price per watt takes a hike upwards for these. You may find that the T-105s last longer than their peers too because they are in the same case but have smaller plates so can afford to shed more active material to the bottom and not suffer from soft shorts.

I've a pair of Crown 6 volts, were running everyday for a year; discharge between C100 and C20 charging between C50 and C5. Since moving into a concrete house I probably only run them for 2-3 months a year the last year. I've one cell that's a bit slow; -0.01 SG than the others since months after I bought the set which is only apparent after charging and gets to 1.280 a few days on float after the rest. I've put it in the middle of the bank and the capacity is bang-on rated.

A dead cell in a motorhome is pretty uncommon, they tend to have an easy life of it; working weekends and floating all week. I never have to equalise mine anymore, if I'mliving on them I have absorption set to 14.8V and if they're idling 14.1V. Pretty blooming hard find a good charger with a 14.8v set point.  banghead
Excepting those poor unloved souls that get tied to a parasitic load 10 months a year occasionally zapped with an under-wired alternator and run until the incandescents go yellow.  freeze
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guydewdney
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« Reply #5 on: August 25, 2015, 10:26:25 PM »

Ok. Bank manager had some valium. Batteries ordered.

charging.
If i stick the engine one's on charge, with a vsr set to connect the banks togther when the eng ones are 'charged'  will my 14a ctek 24v charger cope? Assuming both banks are 90%+ charged at the outset.

Or do i need 2 x 24 chargers? Eek.
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Scruff
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« Reply #6 on: August 25, 2015, 11:04:54 PM »

VSR you say.

Here's a good one;
http://www.ebay.co.uk/itm/MERLIN-Smart-Bank-Split-Charge-Management-System-12V-DC-/111653486772?hash=item19ff1100b4
[Edit: I know it's listed as 12v but the Smartgauge website says it's 12v/24v same unit]

This seller has 3 going for £15 plus postage and the 12V Merlin badged Albright relays whenever he's back from holidays, although any relay will do as long as it's within spec +20%.
http://www.ebay.co.uk/usr/kalvariskis?_trksid=p2055119.m1438.l2754

They're very unforgiving if you wire them live though...no reverse numpty protection.


The Ctek can run all day long, I think they reduce output as thermal management. Maybe check the manual.
Problem is it's going to be slow (which is actually very good for the battery if you can afford the time).
My biggest gripe with Ctek is they aren't designed for flooded batteries, you won't get 29.4v temp compensated outtov it, so less watts and lower potential difference means more time, less water loss and possibly more sulphates except that it does some fancy what-have-yous to prevent this.

Most people recommend a C10 charger so a 25A charger would be normal fitment for a 225Ah house bank + starter battery.
I'd not bother with a bigger mains charger than you already have though, I have loads of them and I've decommissioned them all in favour of solar controllers.
I'd get a 250W domestic VOC 36V PV module on the roof, and a good PWM solar controller and if you still need more electrons after that I'd put a current limited power supply through the solar controller or upgrade the alternator wiring or both.

Best only use one charging source at a time or they confuse each other.

Another problem with split bank charging is one bank raises the other bank's voltage fooling the charger into thinking the bank has a higher SOC than it really has.
One way around this is put the chargers on the house bank and rely on voltage drop to assuage the misinformation. The best way is to run two isolated systems. Starter batteries don't get cycled very deeply anyways they take very little to charge usually.

 tomatosplat Simple answer to the question Guy is yes your Ctek will cope. You may have to water your starter battery more often as it will be held at absorption volts no current after it has finished charging as long as the house bank remains on charge across the VSR.
« Last Edit: August 25, 2015, 11:57:32 PM by Scruff » Logged
knighty
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« Reply #7 on: August 26, 2015, 03:27:22 AM »

when you have a 24v truck anyway, can't yo just wire in a relay to connect the engine and leisure batteries together when the engine is running ?

alternator can put out more than enough amps to charge both at the same time anyway

simpler system, with less to go wrong ?


for my camper van I bought a relay from an electric forklift, 12v and 500amps.... so if I ever run the engine battery down I can press a button, the relay engages and I can use the leisure batteries to give the engine batteries a boost :-)
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guydewdney
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« Reply #8 on: August 26, 2015, 08:23:27 AM »

I have a marine grade vsr, with manual override option. Carries 1500a (for 3 seconds) with remote operation. I was looking at wiring this onto the starter battery, so that when the engine is running its over ?27?v the relay engages, and parallells the two banks.

But, if the charger is on the starter batteries on float (ie over the winter) the relay engaged, should the leisures be ok?

I have a solar panel on the roof, about 250w. Goes to a steca 10.10f module, wired to the leisures.

Is the steca too dumb to be left on 24/7/365? Cos my 2 yr old sealed lead acid batteries (approx 85ah each) x 4 are now less than 10ah capacity each. No known parasitic loads. Steca showed it was in a sort of float mode (green light flashing).
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fourfootfarm
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« Reply #9 on: August 26, 2015, 08:30:39 AM »

I made a google spreadsheet a little while ago with all the different battery choices I could find.

https://docs.google.com/spreadsheets/d/1eHe5Pb7kKhWIrzW1JGnrVCJSIIa1O1V8kGQ2q9pskX0/edit?usp=sharing

Its a bit out of date now but gives you a rough idea.
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Outback FM60. EPsolar 30a MPPT and a bunch of Tristar 45's. Hodge Podge of solar ~ 4500w. Various generators and 1000ah 24v forklift battery.

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guydewdney
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« Reply #10 on: August 26, 2015, 10:17:41 AM »

Thanks peeps. New batteries ordered from batterymegastore.
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oliver90owner
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« Reply #11 on: August 26, 2015, 10:39:22 AM »

You've just missed the bargain of the year from reeeooow? (See his recent sales thread).  Shame on you! Smiley
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Scruff
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« Reply #12 on: August 26, 2015, 01:54:07 PM »

In my experience people usually overestimate the ability of an alternator to charge an auxiliary bank. It's designed to supply running loads not to charge a cycled battery. The output is stock limited to the gauge of the wiring loom.
The voltage drop caused by too thin wiring and being tied to a charged starter battery limits the charge current significantly. It can be seen that roughly the square of the ampacity of charge is reduced proportional to the difference of the voltage.
I had a 55A alternator with a 12mm² battery interconnecting lead through a relay and the most charge current I ever saw was 16A. I swapped the alternator for a 150A, upgraded the stock loom from 8mm² to 35mm² to the starter, 50mm² to the starter battery and 90mm² to the aux bank. I now get >40A charge to the aux. bank.  It's still just a constant voltage single stage charger. It's only good for bulk charging, I need PV to fill the gaps.
Better would be to start the motor from the engine battery and route the alternator to the aux. bank first and starter battery second. Even better still would be two alternators.

I don't know Steca controllers, I was turned off by the inaccuracy of their SOC function..basically just a voltmeter. A 10A controller on an 9A module seems a bit underrated, there's supposed to be 25% overhead for cloud edging. Can't say whether it's up to the task without soak testing it. Ideally it'd float at ~27V with < 300mA after load compensation and persist at charging until the SG is ≥ 1.275 then trickle the current down to ±0A


But, if the charger is on the starter batteries on float (ie over the winter) the relay engaged, should the leisures be ok?


Yeah they'll be 'right. Reason I'm saying to put the charger on the house bank side is they're a much bigger bank and more heavily cycled. The charger reads the voltage from the charging leads so it's less incorrect charge the starter battery from a charging house bank than vice versa.

To measure a parasitic load just switch off all loads disconnect a battery clamp and put an ammeter in line between the battery clamp and the batery post (+ive or -ive doesn't matter). If it's over 50mA it's high.

I'd recommend installing an externally shunted panel mount volt + ammeter anyways, they're indispensable, they're pretty cheap on eblag I'd get one with an adjustable trim pot so you can calibrate it from a good meter before installing. Most people use voltmeters to monitor the batteries, I think the ammeter gives a much better picture of what's going on. Better still is an Ah counter SOC meter with these features integrated but they do drift out of sync so it's debatable whether they're worth the dosh.  

Here's a rather long winded exploration of the practical development of my system.
http://www.boards.ie/vbulletin/showthread.php?t=2056946527
« Last Edit: August 26, 2015, 09:36:53 PM by Scruff » Logged
Nickel2
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« Reply #13 on: August 26, 2015, 02:16:06 PM »

Didn't Frotter bodgineer some sort of contrivance for using ordinary alternators to charge 24V? (Or was it 48V, can't remember).
Time to trawl back through the older posts I think.
N2
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1.140kW mono south-facing at 49*
EpEver 4210A at 24v
24V 400 Ah battery. (4x200Ah FLA)
EpEver STI1000-24-230 pure sine inverter
Of course it'll work. (It hasn't caught fire yet).
Scruff
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« Reply #14 on: August 26, 2015, 02:30:44 PM »

2 x 24v in series with the ground lifted to produce 48V.  Grin
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