Advice sought re. battery replacement

[Froggy]

Series is simple. Pos from batt 1 to Neg of batt 2. You now have 12V between Neg of batt 1 and Pos of batt 2.

 

If you have another pair (3 & 4) you connect the top Pos's together and the bottom Negs together and you've put them in parallel.

 

Paralleled batteries will (if of equal size and charge) split the load 50:50.

 

(Three bats in parallel will share the load 33:33:33, Four 25:25:25:25 etc)

You've partly clarified this for me - but not completely! If you look at this diagram here, http://www.countybattery.co.uk/latest/2015/01/seriesandparallelconnections/ only one of the four batteries in the third diagram is connected positive to negative (to double the voltage), whereas in my bank of four this is doubled up (positive of 1 to negative of 2, positive of 3 to negative of 4). So is one of these connections in my bank superfluous?

Edited January 22, 2017 by Froggy

[Froggy]

 

In the OP's photo the load would be more equally shared between the two pairs of batteries if the red wire to the rest of the boat was connected to the other end of the long red bridging link. i.e. move the wire arrowed to connect to the terminal circled.

 

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Your comment re the load is interesting because it's battery 4 that is bubbling. So from what you're saying it's because the existing configuration is allowing a charge to flow from battery 2 to the engine bay but also from the positive of battery 4 to the negative of battery 4 as well, yes?

 

To operate with 2 T105s you would just "cut down the middle" ie remove the two LH batteries and disconnect and remove the long leads that link the LH and RH pair.

 

If you want to run two 12v batteries you just connect their +ves together, connect their -ves together, and connect the long leads from the boat to a +ve on one battery and the -ve on the other (to help balance the current flowing in and out of the batteries).

 

Thanks to both of you. This is all slowly starting to make sense.

Edited January 22, 2017 by Froggy

[WotEver]

You've partly clarified this for me - but not completely! If you look at this diagram here, http://www.countybattery.co.uk/latest/2015/01/seriesandparallelconnections/ only one of the four batteries in the third diagram is connected positive to negative (to double the voltage), whereas in my bank of four this is doubled up (positive of 1 to negative of 2, positive of 3 to negative of 4). So is one of these connections in my bank superfluous?

No. you have 6V batteries. So you have a pair connected in series to give 12V (batts 1 & 2). Then you have another pair connected in series to give 12V (batts 3 & 4).

 

So now you effectively have two 12V batteries which can be connected in parallel (+ to + and - to -).

 

Clear now?

[MtB]

 

Your comment re the load is interesting because it's battery 4 that is bubbling. So from what you're saying it's because the existing configuration is allowing a charge to flow from battery 2 to the engine bay but also from the positive of battery 4 to the negative of battery 4 as well, yes?

 

 

No, David's suggestion is a case of finessing an already good and working installation. Although technically correct it will make in practice no discernible difference.

[Froggy]

 

 

No, David's suggestion is a case of finessing an already good and working installation. Although technically correct it will make in practice no discernible difference.

 

 

No. you have 6V batteries. So you have a pair connected in series to give 12V (batts 1 & 2). Then you have another pair connected in series to give 12V (batts 3 & 4).

 

So now you effectively have two 12V batteries which can be connected in parallel (+ to + and - to -).

 

Clear now?

I think so, but this would seem to be at odds with David's suggestion in post #24, because surely then the lead to the engine bay would have to come off battery 4 rather than battery 2 in order to double up the capacity?

[MtB]

 

 

I think so, but this would seem to be at odds with David's suggestion in post #24, because surely then the lead to the engine bay would have to come off battery 4 rather than battery 2 in order to double up the capacity?

 

 

But those two terminals are already connected togther with a hefty cable of effectively zero resistance so it doesn't matter wich end of it you connect the power take-off cable.

 

In reality the interconnect has a measurable (but very VERY tiny) resistance so it is better in theory to fit the draw off cable at the end David suggests.

[Froggy]

 

 

But those two terminals are already connected togther with a hefty cable of effectively zero resistance so it doesn't matter wich end of it you connect the power take-off cable.

 

In reality the interconnect has a measurable (but very VERY tiny) resistance so it is better in theory to fit the draw off cable at the end David suggests.

 

Ok, thanks for clarifying Mike. Maybe the lead to the engine bay isn't long enough to reach battery no.2. I'll investigate when I disconnect the two unbranded batteries next week as you suggest. I guess that if we can eradicate the bubbling battery there is then less urgency to replace any of them. We're at a marina for the next month or so and it will give us a chance to assess the capacity of the remaining batteries, although i reckon that they won't prove to be particularly healthy.

[AllanC]

As far as i understand the Trojan T-105 batteries have a very high 225ah capacity, giving us a total capacity of 450ah if replaced like for like, compared with probably about half that if replaced with two reasonable quality 12v alternatives, .

Is this correct. Assuming 225ah operated in a 6 volts circuit, then when connected in series to give 12 volts would the ah be doubled to 450ah or still be 225ah at 12v

[cereal tiller]

Is this correct. Assuming 225ah operated in a 6 volts circuit, then when connected in series to give 12 volts would the ah be doubled to 450ah or still be 225ah at 12v

225 A.H.

[nicknorman]

225 A.H.

Yes although the OP's post is a little unclear when he says "like for like" and currently has 4 batteries. So 4 T105s gives you 450AH, 2 give you 225AH (at 12v).

[Froggy]

Yes although the OP's post is a little unclear when he says "like for like" and currently has 4 batteries. So 4 T105s gives you 450AH, 2 give you 225AH (at 12v).

The assumption in my post was based on replacing all four batteries configured in series parallel as per the photograph, so doubling up the capacity. Due to cost we will probably not now do this (we also have a failed toilet pump and immersion element to replace, and the BSS assessment is imminent).

 

EDIT: 'immersion thermostat' is now corrected to 'immersion element'.

Edited January 23, 2017 by Froggy

[Alan de Enfield]

The assumption in my post was based on replacing all four batteries configured in series parallel as per the photograph, so doubling up the capacity. Due to cost we will probably not now do this (we also have a failed toilet pump and immersion thermostat to replace, and the BSS assessment is imminent).

 

You seem to be having a 'rough' time - were all of these issues picked up when you bought the boat, were you able to negotiate the price down in light of all the costs involved ?

[Froggy]

 

You seem to be having a 'rough' time - were all of these issues picked up when you bought the boat, were you able to negotiate the price down in light of all the costs involved ?

We did negotiate a reduction after first viewing. After the survey the seller wouldn't budge further and we decided to purchase anyway because we liked the boat. The immersion element and toilet pump were working at the time so the failure of these is just unfortunate timing, although with regard to the toilet pump this probably wasn't helped by the fact that we didn't know we had a separate water supply tank for the toilet flush so accidentally put Blue down it, resulting in this being circulated to the toilet via the pump. Edited January 23, 2017 by Froggy

[AllanC]

Yes although the OP's post is a little unclear when he says "like for like" and currently has 4 batteries. So 4 T105s gives you 450AH, 2 give you 225AH (at 12v).

Thanks for clarifying Nick. I misunderstood.

[dmr]

 

 

My bet would be the battery bubbling acid is one of the unbranded ones.

 

As already suggested, try disconnecting the unbranded ones and running on the Trojans alone. They might outperfom the bank of four once you remove the one dragging the bank down.

 

Are we sure that the red ones are unbranded? They look very much like the US Battery equivalent of the Trojan to me, and some folk would rate US as even better than Trojans.

 

................Dave

[Froggy]

 

Are we sure that the red ones are unbranded? They look very much like the US Battery equivalent of the Trojan to me, and some folk would rate US as even better than Trojans.

 

................Dave

Maybe you're right. All will be revealed when I remove them in a few days' time.

[Froggy]

Just to update this topic, the two troublesome batteries were removed from the circuit and the other two are performing satisfactorily whilst hooked to our marina hookup. Whether they will suffice when we're out on the cut remains to be seen. Incidentally, if you look very carefully at the photograph in post #11 you will see a thinner red cable that wasn't connected up. I only noticed this myself when i came to disconnecting the batteries and have left this disconnected (and taped it up!) until i investigate further, but any suggestions are welcome. Attached is a photo of the disconnected batteries showing brand name. Many thanks for all those who contributed to this thread.

[Neil Smith]

As you are on mains power is your charger able to do an equalisation charge of 15+ volts to desulphate them and regain there capacity.

Neil

[MtB]

14 hours ago, Froggy said:

Just to update this topic, the two troublesome batteries were removed from the circuit and the other two are performing satisfactorily whilst hooked to our marina hookup. Whether they will suffice when we're out on the cut remains to be seen. Incidentally, if you look very carefully at the photograph in post #11 you will see a thinner red cable that wasn't connected up. I only noticed this myself when i came to disconnecting the batteries and have left this disconnected (and taped it up!) until i investigate further, but any suggestions are welcome. Attached is a photo of the disconnected batteries showing brand name. Many thanks for all those who contributed to this thread.

Thanks for the update. 

That's a very neat removable cap design on those old batteries. Releases all three caps in one simple movement! I bet they fit your Trojans, I suggest you hang on to those. 

[Leon 12]

The interconnects are rusty which ain't good and also the load via cables wasn't split. Both pos and neg were off the right hand pair, like you all have said he might get better results  from just the Trojans

[Froggy]

On 28/02/2017 at 08:00, Neil Smith said:

As you are on mains power is your charger able to do an equalisation charge of 15+ volts to desulphate them and regain there capacity.

Neil

I don't think our Victron has that capabilty, but one of the connection terminals sheered off anyway when i removed the lead so these are now scrap.

[Froggy]

On 28/02/2017 at 08:22, Mike the Boilerman said:

Thanks for the update. 

That's a very neat removable cap design on those old batteries. Releases all three caps in one simple movement! I bet they fit your Trojans, I suggest you hang on to those. 

Thanks Mike, will do, and apologies for the late reply. Btw, they're also pretty strong too - i lifted the first battery out of the tight space with this before noticing the warning on it not to do so!    A bit of good news: the boat passed the BSS.   

 

On 03/03/2017 at 16:29, Leon 12 said:

The interconnects are rusty which ain't good and also the load via cables wasn't split. Both pos and neg were off the right hand pair, like you all have said he might get better results  from just the Trojans

It wasn't possible to rectify this because the positive lead was too short to reach over to the left hand pair.

Edited March 30, 2017 by Froggy

[Alan de Enfield]

15 minutes ago, Froggy said:

I don't think our Victron..................

My Victron charger can do a 15.2v charge by 'toggling' the up/down buttons (the ones alongside the power / standby switch), but can be adjusted up to 16.0 volts in 0.1v increments

[Froggy]

4 minutes ago, Alan de Enfield said:

My Victron charger can do a 15.2v charge by 'toggling' the up/down buttons (the ones alongside the power / standby switch), but can be adjusted up to 16.0 volts in 0.1v increments

I'll take another look but ours is 20 years old and was part of the original kit.

Incidentally, a guy doing some electrical work for us (blown immersion element) reckoned the 240v sockets don't seem to have an earth when run through the inverter, i.e. shorting the terminals doesn't trip the rcd. He reckons it's potentially dangerous and possibly an issue with the inverter, although the original boat manual states that it's safeguarded against shocks. I need to do a bit of research into this.....

Edited March 30, 2017 by Froggy

[MtB]

On 30/03/2017 at 22:08, Froggy said:

I'll take another look but ours is 20 years old and was part of the original kit.

Incidentally, a guy doing some electrical work for us (blown immersion element) reckoned the 240v sockets don't seem to have an earth when run through the inverter, i.e. shorting the terminals doesn't trip the rcd. He reckons it's potentially dangerous and possibly an issue with the inverter, although the original boat manual states that it's safeguarded against shocks. I need to do a bit of research into this.....

 

Hmmm I wouldn't expect this to trip the RCD as this is a device to detect current leakage outside of the primary circuit.

It ought to trip the MCB or fuse though. Assuming you have one. I'd be very wary of his advice as he doesn't seem to grasp the purpose of the RCD.