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split circuit charging on motorhome
theconrodkid - 22/4/20 at 08:29 AM

Friend of mine has a motorhome with three batteries, she charged the engine start battery up and took it for a drive, next morning all three batteries were dead again.
i know a duff battery can cause all three to go flat , the relays are supposed to isolate the batteries to stop this happening ? so i am thinking new relays required ?.
i cant exactly go and have a look as it,s in Tennessee , i dont want her to get ripped off.

britishtrident - 22/4/20 at 09:57 AM

quote:
Originally posted by theconrodkid
Friend of mine has a motorhome with three batteries, she charged the engine start battery up and took it for a drive, next morning all three batteries were dead again.
i know a duff battery can cause all three to go flat , the relays are supposed to isolate the batteries to stop this happening ? so i am thinking new relays required ?.
i cant exactly go and have a look as it,s in Tennessee , i dont want her to get ripped off.


More than possible the engine starter battery has been killed modern starter batteries with calcium doped plates don't take well to being deeply discharged.
Split charge relays will only charge the auxillary batteries once the main battery reaches a certain voltage normally about 13.5v The domestic batteries should be either deep cycle batteries which are old style lead acid or AGM types which should recover from deep discharge.
In reality all three batteries need disconnected and slow charged for 12 to 24 hrs then batteries, charging system and voltage sensing split charge relae tested

[Edited on 22/4/20 by britishtrident]

britishtrident - 22/4/20 at 10:09 AM

These work well they also do a bluetooth version.

https://www.amazon.co.uk/Autool-BT-360-Battery-Testers-Diagnostic/dp/B01NACKGJU/ref=sr_1_16?crid=3JQ1LENL8U8GV&dchild=1&keywords=autool+batter y+tester&qid=1587549800&sprefix=autool+batt%2Caps%2C1849&sr=8-16

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rusty nuts - 22/4/20 at 10:23 AM

First thing to check would be the battery condition followed by the alternator output at the vehicle battery AND the habitation batteries . No charge at the hab battery would indicate a faulty relay depending on the age of the motorhome ,it may not have a split charging relay ,modern motor homes use electronics to do the job . If it has a relay it’s likely to be near the vehicle battery

theconrodkid - 22/4/20 at 10:45 AM

thanks for the replies, i think it,s around 2002 so quite old (Dodge V10 petrol engine ), maybe safest to bite thebullet and get some new batteries to start with, as i said, she takes it to a garage, she is likley to get ripped off.

cliftyhanger - 22/4/20 at 10:55 AM

Before forking out for 3 batteries, it is worth charging all 3 as advised above, then leave for few days and see if they are still fully charged. Besides, there must be a reliable garage available who can test the batteries? Motorhome people tend to know others (unless things are different in that side of the pond?)

britishtrident - 22/4/20 at 02:46 PM

Really important to slow charge each battery for at least 12 hours at a low amps setting --- best on a smart charger for 2 days or even a full week then rest the battery for 12 hours re=test. These little solidstate battery tester work by measuring AC impedance they are simple to use and very effective.

theconrodkid - 22/4/20 at 03:21 PM

ill let her know re the charging, she lives in to boonies, her neighbours probably have a still and live 20 miles away

steve m - 22/4/20 at 03:34 PM

I think I would go back to basics, disconnect the camper van batteries, charge the starter one, and see if it holds its charge
If so, introduce the next one into the equation,

From my caravan days, Leisure batteries for vans etc, do not respond very well to going completely flat, and need a trickle charger to keep its peek up, hence I bought and still have two solar panel chargers

steve