Dreaming of amps and volts - the Smartbank solution

Sad isn't it but since we were last aboard and we have been able to observe the Smartgauge in action and the poor performance of the charging circuit I have had a crash course in volts and amps. I am writing this over a few days to hopefully add in some photos of what I have done and comment on how it works... if indeed it does do what I am expecting.

Not that I know much more of what is a very large subject field, but I do have a better idea of what happens on Percy when the big lump in the middle make pop popping noises.

Brian and Halfie from Harnser and Jubilee respectively gave me good information about the charging side of my boat. It got me reading and better understanding why we were so poorly rewarded by engine charging.

Result is I will shortly be completing  have completed the install of a Smartbank and associated relay split charging system. There are hopefully benefits ....

• Should be as close to lossless as possible
• Gives me an emergency start mode whereby the leisure batteries are added to the start battery for more oomph for the 3 litre lump
• Priority charging for the start battery... it is directly connected to the alternator so this battery gets what it needs before the relay kicks in and gives the charge to the leisure batteries
• Allows the solar charge to get to the starter battery
• More information about the state of charge of the battery banks

Whilst I like the sound of the Lister CS2 as we only need to run it for propulsion and charging. When we are just staying put I want to run it as little as possible to give me the most back into the battery bank. I expect Tony and Jill did a lot of cruising when on the boat and I don't think they had a TV or other gadgetry to power so the simple split charge diode controller to 2 x 85amp/hr batteries was enough.

So the install is complete, not without a few changes and challenges. The major one being the cable thickness needed for the relay. I delved into Canal world forums for advice and got some contradictory information, further confused by advice from Merlin who market the smartbank.

The diode install used AWG5 cable from the alternator and to the respective batteries.

AWG5 is 16mm2 and whilst Merlin said it would be OK, other said it needed to be bigger. My confusion was the load I was working to. The alternator cable is easy.... 70amp, but the two relay cables were confusing, firstly I confused the total storage (220a/h )with possible current across the relay (its a 180 amp relay) my concern was the emergency start when all three batteries would be connected and supply the starter current, and when I looked at the starter cable I doubted my 16mm2 install.

Cable size information web site

Cable calculator web site

Roger from the forum gave me some good advice and after installing the AWG5 I swapped it all over again. On Percy Tony had installed one of these....

It is a 1600w motor driven inverter...I thought it was old scrap.... until I looked it up on the Internet and they are still for sale for $2,200 !! I have used one of the cables... see below, and I was not intending putting it back, but having read about them i will put it back as it may well be useful for the vacuum and the chainsaw... more experimenting!

Anyhow the cable that services the Redi-line was cut up in the required lengths...(note the workshop again)

I took it to Streethay and they kept up the thousand pound Ray approach by charging me £15 to have four terminals crimped on!!! Note to self, avoid Streethay in the future.

Back at the boat some fitting, refitting and modification of the battery box cover eventually saw my install made with 50mm2 cable throughout. I went for this after reading Tony Brooks excellent site on this area whereby he said extra large cable on such an install only downside was the price of the copper.

So old and new side by side...

Sterling split charge diode on the left (out) Smartbank and relay on the right in.

Work in progress, I moved the isolator up from where you can just see the relay install (this pic was when the 16mm  cable was in use)

When the 16mm cable was used I was pleased to see this....

 

This was compared to 13.5v with the split charge diode controller. The result was it took about 45 minutes to add 8% to the batteries compared to 3 hours to get just 13% back into the batteries. So that is twice as efficient and much more what I was expecting.

After I fitted the 50mm2 cables I got this...

So I have to assume the smaller cables were introducing resistance (heat a by product although not evident !!) and therefore less charge.

So from these....

And then these

I get this...

A good deal of learning, a better charging system plus understanding of my 'other inverter' means all very worthwhile.