Adding Lithium capacity to our existing setup

[chris-s]

Coming back to this as I got sidetracked with other projects for a bit.

Following the advice that what I really need is more solar, my current plan is:

Keep my existing 2 x 110Ah AGM domestic batteries for now.

Upgrade the 30W solar panel to this 100w Renogy item, with a pole / tilt mount.

Replace the existing MPPT controller with this Renogy combined MMPT controller and DC-DC charger.

Connect that to the domestic bank, engine battery and solar panel, using 60A mega fuses for the batteries and a 10A inline fuse between the panel and the MPPT controller.

Upgrade my existing Victron mains charger to a 20A IP22 with Bluetooth (I hate the fact I can get zero info from the current one).

Connect that mains charger to the engine battery (with a 80A mega fuse), and rely on the DC-DC charger charging the house bank when there’s not enough sun and the boat’s plugged in.

My thinking is this will allow me to drop in Lithium batteries when my AGM ones wear out.

Can anyone see any major flaw(s) in the plan? All advice gratefully received as always.

We have the same panels, victron and renogy chargers wired the same way (different fusing and with lithiums) and it works great. We dropped in the lithiums, with a little rewiring, when the agm’s gave up using the same basic charger setup, just changed the battery type in the renogy.
What are you going to use to monitor the charge state? You can use the renogy Bluetooth adapter with the phone app or one of their displays. We opted for the one core which allows for remote monitoring.

 

[PaulRainbow]

I like Victron but you have to admit the Renogy DC-DC/MPPT would save a fair chunk of money so it's tempting, if you're starting from scratch. Do you have any experience of them?

Not directly. I only fit Victron solar controllers, chargers, DC-DC chargers etc. They work well, are reliable, very configurable and can work together over a Bluetooth network. I don't like the idea of a combined MPPT/DC-DC charger, i would prefer separate units for redundancy and to be able to configure each one with its own settings. If you are buying close to £1000 worth of kit for a Lithium installation, which is going to be there for many years, a £200 ish saving, at the expense of the above, doesn't make sense to me.

 

[mrming]

We have the same panels, victron and renogy chargers wired the same way (different fusing and with lithiums) and it works great. We dropped in the lithiums, with a little rewiring, when the agm’s gave up using the same basic charger setup, just changed the battery type in the renogy.
What are you going to use to monitor the charge state? You can use the renogy Bluetooth adapter with the phone app or one of their displays. We opted for the one core which allows for remote monitoring.

I have an existing NASA BM-1 which I was planning to retain for now and replace when we get to adding the Lithium.

 

[john_morris_uk]

We fitted a battery from Epoch Batteries.
12V 460Ah V2 Elite Series - Heated & Bluetooth & Victron Comms LiFePO4 Battery
They ship to Europe but I can’t see UK in their options (I’ve written and asked.). They’re approved by Victron and will talk to the Victron gear, but in our setup we have a Victron shunt which is more accurate.
All Victron makes a lot of sense as it really does integrate extremely easily.

Agree with all that’s been said about fitting extra solar.

Why not fit the slightly larger 50 Amp DC-DC charger? The alternator is capable of supplying the current and the Lithium batteries will suck it up (and more) and you charge that much quicker.

 

[mrming]

We fitted a battery from Epoch Batteries.
12V 460Ah V2 Elite Series - Heated & Bluetooth & Victron Comms LiFePO4 Battery
They ship to Europe but I can’t see UK in their options (I’ve written and asked.). They’re approved by Victron and will talk to the Victron gear, but in our setup we have a Victron shunt which is more accurate.
All Victron makes a lot of sense as it really does integrate extremely easily.

Agree with all that’s been said about fitting extra solar.

Why not fit the slightly larger 50 Amp DC-DC charger? The alternator is capable of supplying the current and the Lithium batteries will suck it up (and more) and you charge that much quicker.

The DC-DC charger I’m planning to fit is 50A, assuming I don’t crack and spend yet more to fit all Victron, in which case I’ll look for that output. Lithium batteries will be a later addition.

 

[john_morris_uk]

The DC-DC charger I’m planning to fit is 50A, assuming I don’t crack and spend yet more to fit all Victron, in which case I’ll look for that output. Lithium batteries will be a later addition.

My bad. I thought I’d read you were planning on a 30 amp one.

We have the 50 amp one and it works brilliantly. Detects when the engine is on and charges the domestic bank. I’m sure you’ll remember to size the cables appropriately. At the currents we’re talking about things get warm very quickly.

 

[mrming]

My bad. I thought I’d read you were planning on a 30 amp one.

We have the 50 amp one and it works brilliantly. Detects when the engine is on and charges the domestic bank. I’m sure you’ll remember to size the cables appropriately. At the currents we’re talking about things get warm very quickly.

I’ve done a bit of reading of the various products' manuals and I think I have the cable sizing right.
For the mains charger to the engine battery: 16mm² 110A cables and a 80A mega fuse.
For the MPPT / DC-DC charger to the house bank and engine battery: 10.0mm² 70A cables and 60A mega fuses.
For the other side of the MPPT going to the panel, Renogy's own extension cable and a 10A inline fuse.

 

[PaulRainbow]

I’ve done a bit of reading of the various products' manuals and I think I have the cable sizing right.
For the mains charger to the engine battery: 16mm² 110A cables and a 80A mega fuse.
For the MPPT / DC-DC charger to the house bank and engine battery: 10.0mm² 70A cables and 60A mega fuses.
For the other side of the MPPT going to the panel, Renogy's own extension cable and a 10A inline fuse.

I wouldn't fit the mains charger to the engine battery. It's charging will be dictated to by the engine battery, so you could have a fully charged engine battery, on float, with a depleted Lithium battery, not being charged.

 

[mrming]

I wouldn't fit the mains charger to the engine battery. It's charging will be dictated to by the engine battery, so you could have a fully charged engine battery, on float, with a depleted Lithium battery, not being charged.

Okay interesting. I thought the charge would flow via the DC-DC charger to the domestic bank, discharging the engine battery which would then get topped up again by the mains charger. Are you saying connect the mains charger to the domestic bank?

 

[john_morris_uk]

Okay interesting. I thought the charge would flow via the DC-DC charger to the domestic bank, discharging the engine battery which would then get topped up again by the mains charger. Are you saying connect the mains charger to the domestic bank?

The engine start battery should barely need charging. Even a prolonged starting of the engine only takes a slack handful of aH out of it which is soon replaced.

 

[PaulRainbow]

Okay interesting. I thought the charge would flow via the DC-DC charger to the domestic bank, discharging the engine battery which would then get topped up again by the mains charger.

The DC-DC charger will only function when the input voltage reaches a pre-set voltage, typically about 14.0V, which only happens when the input battery is on charge, normally when the alternator is charging. The mains charger will charge the engine battery and then go into float, which will be below the start threshold of the DC0DC charger, so it will cease charging, no matter the SOC of the Lithium battery. So the engine battery will never fall to the level the mains charger needs to trigger a bulk/absorption cycle and the DC-DC charger will never work again. It may well be that the charger periodically goes back to a bulk charge, but it isn't likely to be long enough to charge the Lithium battery.

There are some possible events that may vary the above, but it's not a reliable way to maintain the Lithium battery.

Are you saying connect it to the domestic bank?

Yes, but you need to set the charger for a Lithium profile. Exactly what charger do you have ?

 

[mrming]

The DC-DC charger will only function when the input voltage reaches a pre-set voltage, typically about 14.0V, which only happens when the input battery is on charge, normally when the alternator is charging. The mains charger will charge the engine battery and then go into float, which will be below the start threshold of the DC0DC charger, so it will cease charging, no matter the SOC of the Lithium battery. So the engine battery will never fall to the level the mains charger needs to trigger a bulk/absorption cycle and the DC-DC charger will never work again. It may well be that the charger periodically goes back to a bulk charge, but it isn't likely to be long enough to charge the Lithium battery.

There are some possible events that may vary the above, but it's not a reliable way to maintain the Lithium battery.

Yes, but you need to set the charger for a Lithium profile. Exactly what charger do you have ?

Okay great - thanks for the clear explanation. Remember I’m sticking with the existing Lead Acid for now and will drop in Lithium later. Planning to upgrade to the Victron IP22 mains charger with Bluetooth.

 

[PaulRainbow]

Okay great - thanks for the clear explanation. Remember I’m sticking with the existing Lead Acid for now and will drop in Lithium later. Planning to upgrade to the Victron IP22 mains charger with Bluetooth.

Perhaps just fit a Victron solar controller for now and leave the existing mains charger as it is. When you go Lithium fit a Victron DC-DC charger and a new mains charger.

 

[mrming]

Perhaps just fit a Victron solar controller for now and leave the existing mains charger as it is. When you go Lithium fit a Victron DC-DC charger and a new mains charger.

Yes this could well be the answer. Everything else already works and stays the same for now. Thanks Paul!

 

[paulbrown22]

The DC-DC charger will only function when the input voltage reaches a pre-set voltage, typically about 14.0V, which only happens when the input battery is on charge, normally when the alternator is charging.

Is that still the case if you have one of the external "smart" alternator regulators, or they generally enter a "float" of < 14.0V?

 

[PaulRainbow]

Is that still the case if you have one of the external "smart" alternator regulators, or they generally enter a "float" of < 14.0V?

If you have a smart regulator where you can configure the setting, connect it to the Lithium battery.

 

[paulbrown22]

If you have a smart regulator where you can configure the setting, connect it to the Lithium battery.

And then you'd do a "reverse" DC-DC charger from the Lithium to the start battery to keep it topped up?

And/Or if the "smart" regulator isn't smart enough to switch to a Lithium profile, then just ditch it, revert to traditional alternator regulator charging the start battery, and DC-DC charge the Lithium?

 

[john_morris_uk]

If you have a smart regulator where you can configure the setting, connect it to the Lithium battery.

Assuming it’s smart enough to have a Lithium setting?

 

[PaulRainbow]

And then you'd do a "reverse" DC-DC charger from the Lithium to the start battery to keep it topped up?

And/Or if the "smart" regulator isn't smart enough to switch to a Lithium profile, then just ditch it, revert to traditional alternator regulator charging the start battery, and DC-DC charge the Lithium?

Can't answer those questions without knowing exactly what you have and how it can be configured.

 

[PaulRainbow]

Assuming it’s smart enough to have a Lithium setting?

Yes, something suitable for Lithium.

It's worth noting that a Lithium profile isn't a million miles from wet lead acid and you can also use different settings for MPPT, shore charger and DC-DC charger, all on the same system, depending on the pattern of use.