new battery time again

[Harrytherid]

I have been doing some research. Apparently the Ouhoug SCR that I have is a smart isolator in that it gives the battery just what it wants which at the moment, as mine is nearly fully charged, is just 3 amps so |I have no further worries there.

 

[merl]

I have been doing some research. Apparently the Ouhoug SCR that I have is a smart isolator in that it gives the battery just what it wants which at the moment, as mine is nearly fully charged, is just 3 amps so |I have no further worries there.

Hmmm, I'd like to know how on earth an SCR can possibly know the manufacturers charge limit of a battery and "give it just what it wants" That truly IS a smart piece of apparatus .
Seriously Harry that ain't going to happen, don't rely on it to keep the charge current below 20A.
Current naturally drops as the SOC increases when charging from a constant voltage source (your alternator) so your SCR isn't performing anything intelligent at all, it's marketing BS. Believe me, with your system AS IS you'll exceed 20A charge current into a reasonably discharged battery.

 

[Harrytherid]

I am currently discharging the battery so I can check that. Once down to 10v I shall recheck. Thanks for the heads up but maybe 20A is a general limit, who knows, Anyway I am checking to be sure.

 

[merl]

I am currently discharging the battery so I can check that. Once down to 10v I shall recheck. Thanks for the heads up but maybe 20A is a general limit, who knows, Anyway I am checking to be sure.

20A isn't a general limit Harry, it's something that's peculiar to that particular battery for sure and may be due to LC technology? If so then anyone with a system like yours and Trev's or has a B2B and going for LC needs to make sure their chosen battery is compatible. In a conventional MH/ caravan setup there's enough resistance in the system wiring, connectors, relays, fuses, etc to limit the current substantially, after all there's a (20A?) fuse in that charging circuit so that's an indicator of the expected current so I wouldn't expect an issue? Maybe there is??

 

[trevskoda]

How about fitting another battery to split the alts charge down a bit between say 3/4 batts, on my yogie that would be 20ah into each.
My problem and i solved it was the fan belt would and did snap due to a sudden big load, so after going a we bit down the road at higher revs i hit the switch and all is well.
I have been thinking of getting all the pulleys of the later van which are the wide multy rib type.

 

[Nabsim]

I knew you couldn’t charge lead carbon as quickly as say lithium but I didn’t realise they were charge limited like that. Is that all lead carbon or just that brand?

 

[Nabsim]

Is Trev’s system not cable from alternator to starter battery then cable from starter to leisure battery? Not really thought about it but I thought that was the correct way and stopped full amp charging due to battery resistance.

Edit: thinking about it though that’s why you would limit charging by reducing cable size and increasing cab,e length so my initial thought was wrong. Great having goldfish brain

 

[merl]

I knew you couldn’t charge lead carbon as quickly as say lithium but I didn’t realise they were charge limited like that. Is that all lead carbon or just that brand?

Dunno Neil, I only stumbled across it because I used a pair. They are certainly quite secretive about it, nothing in the sales bumf and nothing in the technical PDF either, just a sticker on the battery. As it happens I had a 40A B2B so it was fine with 2 batteries in parallel. As I've said in a conventional system I think things could get close but folks would probably be ok? Dunno, never actually measured charge current on a system using a plain old SCR, the wiring resistance would be the governing factor and that would vary depending on how it was converted from vehicle to vehicle.

 

[Harrytherid]

I think perhaps I might put a 20A fuse in the circuit and as long as it is easily accessible and replaceable then I shall protect the battery in the event of a spike. If that becomes a problem then I can look further into providing some suitable resistance. I will get there in the end.

 

[Nabsim]

I think perhaps I might put a 20A fuse in the circuit and as long as it is easily accessible and replaceable then I shall protect the battery in the event of a spike. If that becomes a problem then I can look further into providing some suitable resistance. I will get there in the end.

My Geist came from the factory with a 50amp fuse at either at starter and leisure battery end with a 2 amp fuse piggyback both ends that was d+ for the relay in the EBL

 

[merl]

I think perhaps I might put a 20A fuse in the circuit and as long as it is easily accessible and replaceable then I shall protect the battery in the event of a spike. If that becomes a problem then I can look further into providing some suitable resistance. I will get there in the end.

That won't work Harry. You need to sort something out properly or choose another battery. A 20A fuse will pass well over that for a long time before failing from fatigue.
Have you done that discharge/ charge test you mentioned yet? If so what current did you see at the start?

 

[Harrytherid]

I got the battery voltage down to 10 and the charge rate went up to 8A. It is coming down rather slower now so I think I will put the 20A fuse in and get the battery. If it then continues to drop I shall do some more hunting for a leak. I have nearly had enough for now. Time to get it all back together now.

 

[merl]

How about fitting another battery to split the alts charge down a bit between say 3/4 batts, on my yogie that would be 20ah into each.
My problem and i solved it was the fan belt would and did snap due to a sudden big load, so after going a we bit down the road at higher revs i hit the switch and all is well.
I have been thinking of getting all the pulleys of the later van which are the wide multy rib type.

Yes Trev that would work but like you say with a 80A alt you'd need 4 batteries in parallel to share the current. Cheaper to fit a B2B or simply use a battery with a higher current tolerance.

 

[Harrytherid]

I had sent mine, Merl, before I saw yours. 2A from relay when battery at 12V and 8A at 10V

 

[merl]

I got the battery voltage down to 10 and the charge rate went up to 8A. It is coming down rather slower now so I think I will put the 20A fuse in and get the battery. If it then continues to drop I shall do some more hunting for a leak. I have nearly had enough for now. Time to get it all back together now.

Something wrong there Harry.
Either that current reading is incorrect or you've got something seriously limiting the current, is the battery shot? Have you got the engine revving above tick over?
Trev has a similar system and he can snap a belt the load is so high! Meanwhile you're getting a measly 8A or less????
Something amiss mate. You're not reading the display incorrectly and getting the decimal point wrong? 80A reducing to 20 sounds more likely than 8 reducing to 2!
Start your engine, put your headlights on and measure the charge current going to the starter battery.

 

[trevskoda]

Is Trev’s system not cable from alternator to starter battery then cable from starter to leisure battery? Not really thought about it but I thought that was the correct way and stopped full amp charging due to battery resistance.

Edit: thinking about it though that’s why you would limit charging by reducing cable size and increasing cab,e length so my initial thought was wrong. Great having goldfish brain

No my alt goes to a old school droper diode, then a cable to starter bat and one to footwell les battery as from the makers of the bus, it was only charging 13.6 ish and all the bats when i got it were fooked.
So a double set of 200ah relays where fitted by me to bypass the diode, one charges the starter batt and other relay the les batts, i added a second battery under the sink and run a big battery cable from front les batt to the secont one, i did this because i have a gas/12v water heater under the sink and a inverter plus switch to run my fridge, hope this makes sense so far, so on startup alt charges through the old diode which is a restriction and wont bust my fan belt, once revs are up above 1.200 i flick the relay switch and bingo 14.4/5 v and all batts connected and charging fully.

 

[Harrytherid]

Got to go out to get some stuff for Julie and I am tired so I shall get back to this tomorrow.

 

[Harrytherid]

Something wrong there Harry.
Either that current reading is incorrect or you've got something seriously limiting the current, is the battery shot? Have you got the engine revving above tick over?
Trev has a similar system and he can snap a belt the load is so high! Meanwhile you're getting a measly 8A or less????
Something amiss mate. You're not reading the display incorrectly and getting the decimal point wrong? 80A reducing to 20 sounds more likely than 8 reducing to 2!
Start your engine, put your headlights on and measure the charge current going to the starter battery.

33A going into starter battery. Yes I believe the leisure battery is knackered which was the point of the original post. Definitely not the decimal point. my first thought so checked that. 8A going into leisure battery which is down to 8V. Engine revs seem to make little difference. Maybe I had better go back to ordinary lead acid. Any recommendations? My first thought is Banner which has served me OK in the past and which I know fits. However, needs to be maintenance free as so difficult to access for maintenance.

 

[merl]

33A going into starter battery. Yes I believe the leisure battery is knackered which was the point of the original post. Definitely not the decimal point. my first thought so checked that. 8A going into leisure battery which is down to 8V. Engine revs seem to make little difference. Maybe I had better go back to ordinary lead acid. Any recommendations? My first thought is Banner which has served me OK in the past and which I know fits. However, needs to be maintenance free as so difficult to access for maintenance.

I've checked a few up to the £280 mark and they all have charging current restrictions. This one https://www.alpha-batteries.co.uk/12v-leoch-pure-lead-carbon-plh-c100-deep-cycle-leisure-battery/ has a 30A limit and frankly looks like a superior battery to the cheaper Leoch ones.
The problem with adding resistance to the charging circuit to get you below 20A is that you've got to limit the 20A to when the battery is well discharged and as the battery charges the charge current will fall off meaning the charge time will rise. If you fitted a 20A B2B you'd get 20A continuous reducing the charge time considerably, allow £100 for the B2B plus the 115Ah LC battery and you're under £300, alternatively go for the one above and add enough resistance to keep charge rate at 30A at say 75% discharged, you'd get a reasonably fast recharge from the alternator.
Going back to LA will be cheaper but it probably wont last as long so you'll be swapping it sooner with all the extra hassle that goes with it, I guess it's pays your money and takes your choice.
Good luck with whatever you choose to do

 

[Harrytherid]

Thanks Merl, at my age a LA battery might well outlast me so that is not a problem and can not afford the dearer LC one.. The question remains, however, what is the best low maintenance or even maintenance free LA battery.
Harry