Trojan Batteries for auxiliary bank, what for starter ?

[jonesthenuke]

I am considering options for replacement batteries, in particular the leisure bank and am tempted to install Trojan T105s Whilst this will require replacement of battery boxes etc the overall lifetime/performance gain seems attractive.

 

However I would welcome comments from those who have gone this way. In particular, if I fit Trojans for the leisure bank what do I do with the starter bank, the reason I ask is that I have recently fitted a Smartgauge/Smartbank, thus the banks of batteries spend much time interconnected, however the charging regime of the inverter and the settings of the Smartgauge would be (?) different for the Trojans.

 

So, if Trojans are fitted to the leisure bank do I also fit for the starter bank, or can I retain the starter batteries and if so how should I set the inverter and Smartgauge?

 

 

The set up we have is

 

Engine Gardner 3LW,

Aternators Leece Neville 90A alternators, one per battery bank

Inverter Mastervolt 12/2000

Leisure bank five 110AH 12v "dual purpose" batteries

Starter bank two 110AH 12v "dual purpose" batteries

 

 

 

Edited as posted inadvertently before completion (D'Oh!)

Edited October 7, 2014 by jonesthenuke

[Hawkmoth]

I am considering options for replacement batteries, in particular the leisure bank and am tempted to install Trojan T105s Whilst this will require replacement of battery boxes etc the overall lifetime/performance gain seems attractive.

 

However I would welcome comments from those who have gone this way. In particular, if I fit Trojans for the leisure bank what do I do with the starter bank, the reason I ask is that I have recently fitted a Smartgauge/Smartbank, thus the banks of batteries spend much time interconnected, however the charging regime of the inverter and the settings of the Smartgauge would be (?) different for the Trojans.

 

So, if Trojans are fitted to the leisure bank do I also fit for the starter bank, or can I retain the starter batteries and if so how should I set the inverter and Smartgauge?

 

 

The set up we have is

 

Engine Gardner 3LW,

Aternators Leece Neville 90A alternators, one per battery bank

Inverter Mastervolt 12/2000

Leisure bank five 110AH 12v "dual purpose" batteries

Starter bank two 110AH 12v "dual purpose" batteries

 

 

 

Edited as posted inadvertently before completion (D'Oh!)

If your banks are charged from different alternators simply set them up for the appropriate voltages. ie 14.4 for sealed starts, and 14.8 for the Trojans.

Bob

[jonesthenuke]

If your banks are charged from different alternators simply set them up for the appropriate voltages. ie 14.4 for sealed starts, and 14.8 for the Trojans.

Bob

Bob, yes I could as they are adjustable, but the Smartgauge/bank interconnects the two so I think both banks would get the higher voltage?

 

I assume that Trojans would be OK as starter batteries but I would rather not buy another pair if its not necessary.

Chris

[nicknorman]

Trojans are not designed to be starter batteries and have reduced maximum current so it would be a bad move to spend extra on them. If you get a normal dual purpose leisure battery that is not sealed, for the starter, it will easily take 14.8v without much gassing, due to the calcium. And if it does gas a bit, you can always top it up.

 

I've left our Smartgauge on type 1 with the Trojans. I think that is the best setting but even if not, the type setting is mostly to get the Smartgauge off to a good start as it learns the batteries' characteristics over time.

Edited October 7, 2014 by nicknorman

[Proper Job]

If you have an alternator per bank, why have you got a Smartbank?

 

A Smartbank unit is for split charging both banks from one alternator, or have you parallelled up the alternators first?

[Robbo]

I have mysell a Exide EM1000 for a starter battery, it's a spiral cell so can take a good range of voltages, provide the amps and doesn't self-discharge as much as a standard wet cell starter battery.

 

http://www.tayna.co.uk/EM1000-Exide-Maxxima-AGM-Battery-MAX900-P7503.html

Good read: http://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf

[dmr]

Do not get sealed starter batteries, no real advantage but some disadvantage.

 

Starter batteries and Trojans have essentially the same chemistry and construction, its just that Trojans have much thicker plates, so charging the starter at 14.8 volts won't really hurt it. However as the starter is always at almost 100% it will get "over charged" and so loose some water.

 

I am not sure how Smartbank works but I believe it uses the voltage detecting relay from the Smartguge. If this is set to something like 14.4 volts then I would think the alternators could be paralleled at low voltage to help the bulk charge, then separated at higher voltages to only apply the 14.8 to the Trojans. This is how alternator paralleling should work. There is no point at all at having the alternators joined once the regulated voltage of the lower one is exceeded.

 

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

[smileypete]

Are the existing leisures sealed or non-sealed/'open'?

 

Out of the seven existing ones, are the best two likely to be good enough to be 'cherry picked' for starting duties?

 

cheers, Pete.

~smpt~

[John V]

Although I have an electrical/electronic background I am no battery expert, it being something I have never needed to know much about however.......

 

If the starter battery is only being used for starting and nothing else why use an expensive battery. Ordinary car batteries are designed for this specific job with the ability to supply very high currents for a very short time probably never falling below 90% charge. If you can charge it from its own charging system at a lower voltage, why go to all the expense and complication of doing it any other way? Why not just keep the whole thing completely separate?

[nicknorman]

Although I have an electrical/electronic background I am no battery expert, it being something I have never needed to know much about however.......

 

If the starter battery is only being used for starting and nothing else why use an expensive battery. Ordinary car batteries are designed for this specific job with the ability to supply very high currents for a very short time probably never falling below 90% charge. If you can charge it from its own charging system at a lower voltage, why go to all the expense and complication of doing it any other way? Why not just keep the whole thing completely separate?

I agree with you about the starter battery type. However regarding your last couple of sentences, things are not that simple!

 

On our boat we have a 175A alternator for the domestics and a 45A alternator for the starter battery, which is fine. They are of course kept quite separate. But on the OP's boat he has two 90A alternators. So you could wire it the same as our boat, but then you have one alternator whose output is barely used, and another that is working flat out a lot and could do with being larger. The solution of course is to put both these alternators in parallel which allows heavy inverter loads with engine running and rapid recharging of domestic batteries from a low state of charge. But once you have connected both alternators in parallel you then need to use this combination to charge both batteries - ie the starter and domestic batteries have to be connected together during charging.

 

It is just a function of the engine mariniser, with the best solution being to have an engine with one large and one small alternator, the second best solution is to connect everything together when the engine is running.

 

Why is this engine like this? Well 90A is about the most you can get with an ordinary V belt / normal pulleys. To get higher alternator power requires a more complex and expensive poly-vee belt and pulleys.

Edited October 8, 2014 by nicknorman

[jonesthenuke]

In reply to the general points above (and thanks for all the comments!)

 

Batteries are all non-sealed "dual purpose" types (I forget the brand)

 

Yes, my aim is to choose the best two batterys to retain as the start

 

The Smartbank gives me some gain in charging the leisure bank initially from both alternators

[smileypete]

Could try putting both alts to 14.8V and carefully monitor the start batts to see how they do.

 

If you'd prefer not to, or the start batts gas too much, one possible workaround would be to put a BIG diode between start alt/smartbank connection and the start bat.

 

Then the start alt could put out 14.8V which would best suit the Trojans, but the start batt(s) would only see about 14.3V. Big diodes can be bought as three phase rectifiers with bolt on connections, just connect so three of the diodes are in parallel to get the rated capability:

 

http://www.ebay.co.uk/itm/Vishay-VS-70MT120KPBF-Bridge-Rectifier-Three-Phase-90-A-1200-V-5-Pin-IN-QTY-1-/351185704674

http://www.ebay.co.uk/itm/MDS100-16-3-Phase-Diode-Bridge-Rectifier-100A-Amp-1600V-IND-/111467533682

 

BTW if using a couple of 90A alts to recharge 400Ah of Trojans, I'd be a bit wary of charging them too fast, though they may put out less in normal use. Also Trojans need periodic equalisation charge at up to 15.5V, not always straightforward if 'off grid'.

 

cheers, Pete.

~smpt~

Edited October 8, 2014 by smileypete

[dmr]

Could try putting both alts to 14.8V and carefully monitor the start batts to see how they do.

 

If you'd prefer not to, or the start batts gas too much, one possible workaround would be to put a BIG diode between start alt/smartbank connection and the start bat.

 

Then the start alt could put out 14.8V which would best suit the Trojans, but the start batt(s) would only see about 14.3V. Big diodes can be bought as three phase rectifiers with bolt on connections, just connect so three of the diodes are in parallel to get the rated capability:

 

http://www.ebay.co.uk/itm/Vishay-VS-70MT120KPBF-Bridge-Rectifier-Three-Phase-90-A-1200-V-5-Pin-IN-QTY-1-/351185704674

http://www.ebay.co.uk/itm/MDS100-16-5-Terminals-Three-Phase-Diode-Module-Bridge-Rectifier-100A-1600V-/291262087960

 

BTW if using a couple of 90A alts to recharge 400Ah of Trojans, I'd be a bit wary of charging them too fast, though they may put out less in normal use. Also Trojans need periodic equalisation charge at up to 15.5V, not always straightforward if 'off grid'.

 

cheers, Pete.

~smpt~

 

Unless the OP has really good wiring and an external controller I doubt if he gets anywhere near 180 amps into the Trojans ??? (can the OP tell us please?)

NickNorman is charging his off a 175 amp alternator so it will be interesting to see how his do over the next couple of years, though I am increasingly thinking that Trojans are bomb proof (touching wood, or at least a bit of scumble)

 

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

[smileypete]

Well just covering all bases.

 

Another way would be to put both alts on domestic bank, then big diode and relay to start batt.

 

cheers, Pete.

~smpt~

Edited October 8, 2014 by smileypete

[John V]

Well just covering all bases.

 

Another way would be to put both alts on domestic bank, then big diode and relay to start batt.

 

cheers, Pete.

~smpt~

 

 

That was running that through my mind when read Nicknormans reply to my post, or one of those battery to battery charging modules...I have a feeling they drop about .6 volt (but haven't been and checked)

[jonesthenuke]

Thanks for the replies this is helping me a lot.

 

Regarding the potential charging current into the Trojans, I have only recently fitted the smart gauge so have not made extensive measurements yet, however the other day the batteries were being charged soon after starting the engine in the morning. I wanted to confirm the function of the Smartbank interconnection and measured ~70A from the starter battery side towards the leisure batteries. I did not measure the total current passing into the leisure batteries as that was not the purpose of my check at the time. Whilst I guess the system is capable of providing the total 180A into the leisure batteries, thus would drop as the batteries charge. Part of my thinking on fitting the Smartbank is that it will assist in covering the peak demand from the inverter (2kW) when the engine is running thus reducing battery cycling.

 

What is a reasonable top limit on charging current for the Trojans?

 

The charging current may not be so much of an issue as I willl fit 6 Trojans (so ~675 Ah capacity) IF they will fit in the existing battery space, thus the current per cell will be less. Whilst I have measured the space I have yet to work out if it will fit. Alternatively I will stick with 5*110Ah dual purpose batteries and accept changing them more often but at lower cost.

 

I have considered fitting a set of the 12V Trojans, however the overall cost seems to be significantly higher for the same capacity and does not appear to be cost effective.

 

Edited to add, often on grid supply in marina so equalisation charges should be practicable via the inverter.

 

Chris

Edited October 8, 2014 by jonesthenuke

[nicknorman]

 

What is a reasonable top limit on charging current for the Trojans?

 

 

If only we knew the answer! On the one hand we have Trojan's recommended charging profile which shows 10 to 13% of the AH capacity which, in my case, would be 45A to 58A. On the other hand as you mention, batteries will only take the current they want to take.

 

I find that whilst we get an initial charge of the full 175A on startup in the morning, it rapidly drops so that after 30 mins it is more like 110A. There doesn't seem to be a noticeable temperature rise, although it is hard to tell because the batteries are near the engine and inevitably slowly get warm as the engine bay temperature increases after startup.

 

Whether this rapid charge is actually harmful is unknown at this point since I only got the batteries in April.

[jonesthenuke]

Thanks to all for the advice on this topic. My plan now is to:-

 

Buy 6 off Trojan T105 batteries and install these for the auxiliary bank

Set the Aux alternator to 14.8V for the Trojans.

Set the Starter alternator to 14.4 for the starter batteries

Set the Smart-bank to disconnect on high voltage at 14.3V, thus protecting the starter battery. This should also stop the starter alternator from shutting down on high voltage, at which point the alternator warning light comes on and the tacho drive signal is lost.

 

The Smart-bank will reconnect at 14.3 V when a large inverter load is applied thus allowing the starter alternator to support the auxiliary bank and reduce cycling as far as practicable.

 

It will be some time before I complete this as we do not live on the boat and i will need to make space for the Trojans (new battery compartment required) and sort out the cable modifications needed. I will update this when I have some opertaing experience.