more battery charging issues

[david42]

Take Five has a simple set up with 2 x 12v batteries and a three position switch. The battery charging on shore power is via a domestic battery charger. I left the shore power disconnected for a few weeks over the winter and both batteries went flat. I topped them up with deionised water last week and hooked up the shore power then left them with the charger showing a charge and humming away quietly and the three position switch on 'both'. After 4 days on charge the batteries were still flat although quite warm and making a gentle hissing sound. I took them both out and they only show 8.7 volts, the levels in the cells are as they were after I'd topped them up. I've no idea how old the batteries are, they've been in the boat since I bought her 2 years ago.

So is it just new batteries? Or do I worry about the charger?

David

 

[Talbot]

if you are using a domestic battery charger rather than a stepped charge system, you should not leave it on charge. It will eventually fully charge the battery, and then just continue to try to charge more. this will result in overheating the battery which wil boil of the electrolyte and also damage the battery.

You need to replace the batteries, and either get a marine stepped charge charger, or invest in a timer, so that the charger can run for short periods only.

 

[davidwf]

If you don't want to spend a lot on the charger Gunsons do a good one at £39 it seems to be a two stage charger dropping back to float at the end of initial charge. I've been using one for over 10 years and never had any problems wth it.



details Here

 

[david42]

The batteries were sizzling but the electrolyte levels were still up, is the heat and sizzling still a sign that they're overcharging?

 

[david42]

I've just realised how dumb that last post sounds.

 

[Talbot]

audible indications are not really relevant as they are so imprecise. get a digital voltmeter.

 

[FlyingDutchman]

Why did the batteries go flat after not being on shore power for a few weeks?
Mine have been in the boat over winter and were still full 3 weeks ago.
Before lay-up I charged them full.
I would think the batteries are knackered, unless you left something on to flatten the batteries.

 

[aidancoughlan]

Sterling do a removable marine battery charger with crocodile clips for around £99. (three-stage thingy). More expensive than a car charger I know, but much cheaper than the permanent ones.
I think Merlin do one similar now.

 

[rogerthebodger]

It sounds like that 2 of the cells have short circuited and the voltage you are reading is the voltage across 4 cells.

With the batterys in this condition any charger will cook the remaining cells.

The only to confirm this is reading the voltage across each cell, if connections accessable or to check the SG of each cell with a hydrometer.

 

[gandy]

[ QUOTE ]
Sterling do a removable marine battery charger with crocodile clips for around £99. (three-stage thingy). More expensive than a car charger I know, but much cheaper than the permanent ones.
I think Merlin do one similar now.

[/ QUOTE ] 10 amp model only £60.00 inc VAT and delivery from here. I bought mine from them :

http://www.amperordirect.co.uk/prod_spp_probud12v-10a_charger.asp?MSCID=53

6 amp model is only £35.00

I already had the Gunson charger but it suffers from two problems. Firstly the output is so low - it never puts out more than an amp or so. That may be old age this case. Secondly, it needs to be switched to select "100% charge" or "Permanent Float".

Tony S

 

[Guest]

Halfords Float Charger - 29 quid ....

Excellent bit of kit .... connect to mains via 10 quid timer .... set to hour or two every so many days cycle .... and leave connected to battery ...............