I’d buy a couple of smaller ones and not motorbike ones. Typically drone batteries are a better weight for carrying yourself. Or you can make packs out of 18650 sized cells. You can buy them from vaping shops or recover good cells from spent laptop batteries. Battery cases are available on eBay for pennies.
The 818 (and 817) doesn’t not need 13.8V for full output but only about 10.5V. So 3S Lipo will power one to full output easily. Or a 4S LiFePo.
I got the Drome type 8600 Lifepo4 AH type as it powers like Andy said its light weight carry in sarnie box for its own protection and ran my 10w station for many hours whilst out in feild. But looking to something a tad bigger like a golfing battery 16 to 22AH. Lot bigger longer life.
Start small and when happy with ya done, go bigger, many many ways of doing it, But do take note of LP4s on storage times, chargers how to charge etc not like doing Lead batteries bang them on away ya go. As well make your battery last longer life as LP4’s no cheap but a good investment that needs looking after.
Bit more study and read more into it. Gotta start somewhere.
And enjoy the world of portable in the areas you can visit you not normally see.
Robotbirds have 1.2Ah 4S LifePo4 batteries available for £8.00 at the moment. Easier to build the capacity you require, just connect them in parallel via the balance connector and wrap a turn of insulating tape around the packs to keep them together as one. Lighter, cheaper and more flexible.
For the low level stages there are, IIRC, some 8V regulators. The PA section runs off whatever you connect. So if you apply 13.8V it will give 5/6W and get quite warm. If you connect 11.1V it will give 5/6W and not get as hot. This makes a 3S LiPo great in this case.
There’s even a flat one (2500 mAH) that will fit inside the FT818’s battery compartment. Two or three of those fully charged will keep you going on several activations. I used to reckon to get three summits (30 mins per summit) out of one fully charged one at 5 watts SSB with RF speech compression pushing the output.
You need to be careful when using an 817 with a 11.1V nom Li-Po battery. These batteries can be damaged if their voltage drops below a certain level. Opinions vary but it’s just over 3V minimum per cell (9V for a three cell pack). More is better.
Further to this, experimental results for voltage inputs on my FT817ND were as follows:
As supply voltage is lowered rig dropped out on receive at 7.2V and would not restart with start button.
As supply voltage is raised rig was re-startable at 8.0V.
Rig produced the same 5W RF power output for input voltages between 7.9V and 13.8Vdc.
4) In order to protect 11.1V Li-Po batteries in future, a diode dropper chain was fitted.
Fitted three 1N5404, 3 Amp diodes all in series with FT817ND positive supply line.
Minimum voltage for FT817ND in RX mode upstream of diode chain: 9.4V (FT817ND sees 7.2V and therefore cuts out). Now the Li-Po cannot get dragged below 9.4V (ie 3.13V/ cell).
You are obviously trying to get at me as I am still using my April 2009 vintage 4000mAH LiPOs, though they are no longer on linear amplifier duty. And to think of it, I met someone recently that is still using SLABs for his low power portable operation.
I’m still using my 2009 LiPos. 1 of those and the £2.50 boost converter gives me an RF quiet 13.5V for the 13cms transverter. The 4200mAh LiFePo drives the 817 and that seems to last “indefinitely” in comparison to the old LiPo
I just spotted someone selling 6x 3000mAh 18650 cells and a 4 cell 500mA/1000ma/2000mH charger for LiPo/NiMHs for £33 which seems OK. Classic eBay scuddy vendor though. “Item location Portsmouth UK” but delivery takes “17-25 days” so that sounds like it’s coming from the Middle Kingdom and “We will write lower value on package,usually without taxes and customs problems.” so you are colluding in a tax and duty avoidance scam too.
As you suggest adding a (or multiple) diodes in series with the supply lead can cause the FT817 to see 7.5v while the 3S LIPO is still at a higher voltage at the expense of activation time, but probably worth the modification. I had no problems with my 2500 mAh 3S LIPO cell in the FT817 without any diode, but perhaps I have never run the battery right down.
It’s great having a good battery capacity inside the rig rather than having to carry an extra external battery and the NiCD battery from Yaesu lasted hardly any time at all for me.
Although having external batteries means they are simple to charge when you get home, easy to change during an activation if required and while inside your rucksack the radio cannot be switched on accidentally, as sometimes happens!
This has all been useful advice. I have today taken delivery of a LiPo 3S 5200mAh battery, and a charger. Also got a pack of Anderson connectors so I can convert my ft818nd and the battery to this connector type. Looks like none of my existing crimp tool s work well with these (I have JST, Dupont, green/red/blue insulated terminals etc…but none make a good job). So now I’m after a cheap pair of Anderson crimp pliers.
It keeps your setup clean and the battery door switch lets you disconnect the battery without having to remove it. This is important as a connected internal battery will be drained quite a bit by an 817 sitting on the shelf.
3AH is good for a pretty long single activation, and a second windcamp battery as a backup just in case is quite lite…